The present invention relates to mobile telecommunication switching networks. More specifically, the present invention relates to the interrogation of mobile stations that are statically employed (i.e., immobile), such as mobile stations employed in telemetry applications, and how a mobile telecommunications switching network can take advantage of this immobility to conserve the limited supply of subscriber numbers and to reduce the ever increasing workload on network components such as the home location register (HLR).
Mobile telecommunications networks, such as the Personal Digital Telephone System (PDC) in Japan, and the Groupe Special Mobile (GSM) System in Europe, provide services other than cellular voice services. For example, mobile telecommunications networks now provide messaging services. Messaging services, in general, permit mobile stations to be interrogated using short message packets, wherein the message packets typically include requests, and responses to requests, for non-voice type data. In the PDC system, a well-known short message service (SMS) is employed as a bearer for short message packets. In GSM, a similar SMS is employed as well as a well-known signalling mechanism known as unstructured supplementary service data (USSD).
In one example, SMS may be employed as a bearer for short message packets in a telemetry application. In accordance with this exemplary use of SMS, it is characteristic for a host computer to contact one or more telemetry sites over a mobile link, wherein each telemetry site is supported by mobile station. The host computer uses short message packets to interrogate each of the one or more telemetry sites. The interrogation generally involves a request that each of the sites transmit certain information back to the host computer. For example, a utility company, such as an electric power company, might employ a host billing computer to interrogate electric meters over a mobile link, wherein each of the electric meters are supported by a mobile station. In this example, the billing computer transmits to the one or more electric meters a short message requesting that each meter transmit their current meter reading back to the billing computer. The request includes a unique subscriber number for each meter so that the short message containing the request is properly delivered by the telecommunications switching network. The host computer, upon receiving the requested information, can then automatically bill its customers.
In all mobile telecommunications networks, each subscriber is assigned a unique numerical identity. In the PDC system, the unique numerical identity is called the mobile subscriber number (MSN). The MSN, in turn, includes an access code, an operator code and a subscriber number. In the GSM system, the unique numerical identity is called the mobile subscriber ISDN (MSISDN) number. The purpose of the MSNs and the MSISDNs is to provide each subscriber with a unique address within the PDC and GSM networks respectively. As one skilled in the art will readily appreciated, the MSNs and the MSISDNs are part of the E.164 international number plan. Herein below, MSN and MSISDN are frequently referred to as subscriber numbers, for the purpose of simplicity. In addition to assigning a unique subscriber number to each subscriber, the radio interface between each subscriber and the network is assigned an international mobile subscriber identity (IMSI), in accordance with the E.212 numbering plan. The IMSI is also used for distinguishing between mobile stations operating within a given network.
When a calling party (i.e., the party placing a call) dials a subscriber number (i.e., A MSN or a MSISDN) associated with a called party, the telecommunications network uses the subscriber number to access a subscriber record corresponding to the called party in the network HLR. The subscriber record contains, among other things, the information and procedures necessary for routing calls, short messages, and other services to the mobile switching center (MSC) service area in which the called party is located, and eventually to the mobile station corresponding to the called party. This information may include, for example, a mobile switching center identification number (MSC-ID) or a routing number, and an IMSI. The MSC-ID or routing number is used for routing the call or message to the appropriate MSC which controls the MSC service area in which the called party is located. The IMSI is then used to send the call or message from the MSC to the mobile station.
In accordance with the present state of the art, every subscriber has a unique subscriber number. This is true whether the subscriber subscribes to a cellular voice service or a non-voice service, such as telemetry. Unfortunately, as the demand for mobile services increases, the availability of subscriber numbers decreases. In addition, the increase in demand for mobile services has drastically increased the workload on telecommunications network components such as the HLR. This, in turn, decreases network performance as it takes a longer period of time to access the HLR to obtain the information and/or procedures necessary to locate and service intended subscribers within the switching network. Therefore, a need exists wherein a telecommunications switching network can limit the number of subscriber numbers assigned, thereby preventing the exhaustion of the E.164 numbering plan, and to reduce the workload on network components, particularly the HLR, to prevent network performance degradation.